Apparatus and process for forming piston rings



Aug. 28, 1951 J. c. LINN 2,566,028

APPARATUS AND PROCESS FOR FORMING PISTON RINGS Filed Dec. 2, 1947 3 Sheets-Sheet 1 9 1 i I; il T i i '7 J 62 47 23 4 1 III Z 1Q- 48 53 2Q I. WM h 3 62 J9 ,.||l J I III J? I 22 -56 Iii -15 I 5 if I 13 INVENTQR. j r I k/Zsgv/z/Cluzm, BY 14 F' Aug. 28, 1951 J. c. LINN 2,566,028

APPARATUS AND PROCESS FOR FORMING PISTON RINGS Filed Dec. 2, 1947 3 Sheets-Sheet 2 IN V EN TOR.

JsgvhCZinm BY J. C. LINN APPARATUS AND PROCESS FOR FORMING PISTON RINGS Filed DeC. 2, 1947 s Shegets-SheetS INVENTOR.

cfoagb/v C Lin/n BY @M, M+W

Patented Aug. 28, 1951 APPARATUS AND PROCESS FOR FORMING PISTON RINGS Joseph C. Linn, Hagerstown, Ind., assignor to Perfect Circle Corporation, Hager'stown, Ind.,

a corporation of Indiana Application December 2, 1947, Serial No. 789,196

14 Claims. I

This invention relates to a novel apparatus and process for manufacturing ferrous metal piston rings, and more particularly to an apparatus and process for imparting to the rings their desired ultimate form, that is to say, their out-of-round contour when in their normal or unrestrained state.

It has been proposed heretofore to heat piston ring blanks, of either steel or iron, above the critical temperature and then to shape the ring blanks to the ultimate ring form by means of forming apparatus, the blanks being quenched and the metal being transformed from its austenitic state to its martensitic state during the forming operation. In this regard, I may refer to the Six Patent No. 2,183,358 dated December 12, 1939, which discloses a process by which the ring blanks have the desired shape or form imparted to them by clamping a plurality of the heated blanks against a formed arbor during quenching. The

invention disclosed in this Six patent has merit, but the apparatus is rather expensive to build and maintain, its operation requires considerable care and exactness, and uniformity in results is not fully accomplished because of varying tolerances and characteristics of the individual ring blanks making up the group being formed simultaneously.

The principal object of my invention is to provide an improved apparatus and process which are simple and economical in structure and operation and which more expeditiously, uniformly and perfectly form piston rings to their ultimate desired shape.

Another object of the invention is to provide a novel continuous method for forming the piston rings to their desired shape.

More particularly, I provide a female die-ring, having its interior periphery formed to the desired ultimate shape or contour of the piston ring,

be cooled, as by air, in order to quench the heated ring While being formed. I prefer to provide several expanding ring dies, so that each piston ring may be moved progressively from one expanding ring to another in order to increase the production capacity Of the apparatus While at the same time each ring is individually formed regardless of any variation in tolerances or characteristics of adjacent rings. Furthermore, the side or axial contact between the piston rings causes them to be formed in flat condition. The operation is preferably continuous, a ram being provided to force each heated piston ring, fed to the apparatus, between the female die-ring and the first expanding ring die, the bottom piston ring already in the apparatus being ejected and the others above itbeing moved one step into engagement with the next expanding ring dies.

The formed rings are subsequently given a drawing operation in a fixture and in such a manner as to assure that their diameters are all substantially the same, and that the rings are of the desired hardness.

Other objects and advantages of the invention will become apparent upon reference to the drawings and the accompanying description thereof in which:

Fig. 1 is a perspective view of an assembled heat-forming apparatus embodying my invention;

Fig. 2 is an exploded view, showing the major parts of the apparatus; I

Fig. 3 is a vertical sectional view on the plane including the vertical axis and the ring-guide devices at the front of the apparatus;

Fig; 4 is a perspective view of a piston ring of the type adapted to be formed by the apparatus and process embodying my invention;

Fig. 5 is a plan view of the ring-forming mechanism, shown in section in Fig. 3;

Fig. 6 is an axial sectional view through drawing fixture, and

Fig. 7 is a fragmentary section taken on the line 1-1 of Fig. 6.

My apparatus and process are adapted to form piston rings of either cast iron or steel. The cast iron ring blanks which are molded circularly, may be first roughly turned on the outer face, bored, rough ground on the edges and parted for free gaps as shown in Fig. 4. Steel ring blanks may be formed by winding a steel wire of the proper cross section into a helix and then cutting the helix to form individual rings, or lengths of such wire may be bent into circular shape with the gaps between the ends, as is well known in the art. Finished piston rings are not truly circular. To operate effectively they are made eccentric in contour so that when they are contracted in an engine cylinder they exert the proper pressure throughout their length against the cylinder wall. By my invention the partially finished piston rings are formed to any desired ultimate shape or contour.

The ring-forming apparatus depicted in the drawings comprises generally an arbor press, a set of radially spaced inner and outer formed dies disposed beneath the arbor press to provide an annular piston ring shaping and cooling zone, and a ring-receiving track on to which the formed rings are discharged.

For purposes of illustration, the over-hanging arm of the press frame carries a vertical arbor 6 provided with a rack portion 1 and operable by means of a pinion drive 9 and an arm N, which may be actuated either manually or by any prime mover through suitable connections. A ram head I I, slotted or cut away at I2, is carried on the lower end of the arbor 6.

A die support I3 is disposed beneath the ram head II and is attached to the pressframe 5 by means of a bracket H. A ringdie holder |5 is mounted on the upper surface l6 of the outer wall of the die support l3 and comprises a bottom portion IS, an outer wall l9, and an inner concentric wall which together form an annular fluid passageway IT. The wall 20 projects upwardly, as shown at 2|, to provide a recess or ledge 22 with a flat ring-shaped cover 23 seated on the ledge and on the outer wall 18 and retained in place by means of screws Is A pair of inlet and outlet conduits 24 is provided for the introduction and discharge of a cooling fluicL'such as water.

An outer ring die 25 is firmly mounted within the wall 20 and rests on an inwardly projecting ledge 26 near the bottom of the wall 20. The upper half of the inner wall of the ring die 25 is tapered downwardly and inwardly to the lower half 25 which is vertical and formed, as by boring and grinding, to the ultimate desired shape or contour of the piston rings.

An expanding-die holder 21 is mounted centrally within the outer ring die 25 by means of a vertical axial stem 29 projecting downwardly from the holder 21 and fitting into a central socket 30 in the die support !3. A main expanding ring die 32, having a. gap 3|, and a plurality of auxiliary expanding ring dies 33, having gaps 34, and 36 are disposed or stacked in axial abutment or side contact on a peripherally projecting flange or ledge 31 at the lower portion of the holder 21. The outer periphery of the ring die 32 is tapered inwardly from its vertical face 39 which is form-turned and ground, as are the faces of the ring dies 33. The backs or. inner periphery of the dies 32 and 33 are all form-bored and ground. The upper outer oornersof the dies 33 are rounded off on a radius. The width, i. e., the distance between the parallel flat sides of each die 33, is the same as that of the piston rings 46 being formed to shape. The dies 32 and 33 are formed of steel, hardened and heat treated to afford the proper tension and wear resistance.

For the purpose of augmenting the self-expanding action of ring die 32, I preferably provide two plungers 60 and an interposed coiled spring 6|, which are positioned in a cross bore 64 in the holder 21 (Figs. 3 and 5). The outer rounded ends of the plungers contact the ring die at points 90 from the gap 3|. Fixed pins 63 (Fig. 5) extend through holes in the plungers to limit movement of the plungers.

The resilient ring dies 32 and 33 are radially spaced from the outer die 25 to define the channel 38 in which the piston rings 46 (Fig. 3 are through a pipe 61.

to be formed to the desired shape. A flat vane 40 extends laterally from the holder 21 into the gaps 3|, 34, 35 and 36 in the ring dies 32 and 33 to prevent rotary movement of the latter. A circular plate or cap 4|, having a slotted portion 42 and a central opening 43, is fastened to the upper surface of the holder 21 by means of screws and is centered thereon by means of a stud 44 which projects into the opening 43. The outer periphery of the cap is tapered and form turned. The cap 4| overlies peripherally the expanding ring dies 32 and 33 but permits free radial expansion and contraction of the latter.

A closing and guiding ring 41, having a gap 48 and a flange 49, rests on the cover ring 23 and the upper end of the ring die 25 and has its inner face tapered inwardly and downwardly to the vertical lower wall portion 45 which is form bored. A generally wedge-shaped gap locator 5|, having a bracket portion 52, is fastened by screws 53 on the sealing ring 23 and is adapted to extend into the gap 42 of the cap 4|, into the gap 48 of the closing ring 41 to'prevent rotation of the latter, and also into the gaps of the piston rings 46 as they pass downwardly from the closing ring 41 into the channel 38. Projecting upwardly from the cover ring 23 are pins 62 which are so spaced as to permit the closing ring 41 to shift slightly when necessary to insure that, when the ram is lowered, its head contracts or partially closes the heated piston ring 45 (Fig. 3) and forces it into the channel 38. The outer and inner peripheries of the ram head are form turned and form bored, so that the shape of its flange is substantially that of the formed piston rings.

An outwardly projecting ring guide block 54 is disposed in a recess 55 in the flange 31 in the die holder 21 and is affixed to the latter by a screw 56. The under surface of the projecting portion of the guide block 54 is generally Vshaped, as shown at 50, to interfit with a V-shaped upper edge of a radial web 51 disposed longitudinally in the die support |3 between the central portion and the outer wall thereof. The upper surface of the projecting portion of the guide block 54 is also V-shaped to facilitate straddling of the guide block by the gaps of the piston rings 46 as the latter are discharged downwardly from the channel 38 on to a ring-receiving track 58 which extends downwardly and outwardly and, in effect, forms a continuation of the web 51.

I preferably cool, as by air, the ring dies 32 and 33. To this end, I provide a conduit 55 in the support l3 and holder 21 (Figs. 3 and 5). The conduit comprises a horizontal portion, extending through the web 51, a vertical portion extending to the bore 64, and another horizontal portion extending from the bore to the clearance between the periphery of the holder and the rin die 32. Compressed air is forced into the conduit Most of the cooling air moves through the clearance behind the dies 32 and 33 and escapes at the gaps in these dies.

The piston rings to be formed to ultimate shape are heated in any suitable furnace to a temperature above the critical, say approximately from 1550 to 1600" F., and for a time, say thirty minutes, suflicient to insure uniformity of austenitizing. The heated rings may be individually trans-- ferred, manually or by any suitable automatic means, from the furnace to the closing and guiding ring 41, in timed relation to the operation of the ram head The gap of the transferred ring 46* (Fig. 3) straddles the guide or locator 5|. When the ram head is lowered, its lower formed edge engages the heated ring. {Grand forces it down. between the formed vertical wall of. the. outer: ring die 25 and the correspondingly formed wall 39 of the expandingringdie-iiZ; As the ring 46 is pushed down, itis first contracted by' reason of the tapered; surface forming" the mouth of the guide ring 4.! and as it. passes out of the formed exit portion below the tapered. surface, it engages the tapered. surface; of the outerring die 25 which in turn contracts; or par;- tially closes the piston ring to:the desired sizebut without closing the gap-as. it. moves into its position between the formed surfaces on the dies 25 and- 32', as indicated by the upper;- piston ring of' the; stack shown in Fig; 3. This causes the rings of the stack to be moved down one step, except for thebottom ring which: is moved out of the die 25' so that it drops through the die support it on to the track 58 (Fig. 1), the ring being guided by the guide, 54: and webv 5! over which the gap in the ring moves. The top and hottest ring of the stack is moved into. contact with the first expanding ring die 33 and the second and third rings are moved into con tact with the second and third expanding ring dies as. The fourth ring is moved. out of contact with the bottom ring die 33 and the fifth ring is moved into the lower end of the outer ring die 25.

The outer diameters of the ring' dies 32 and. 33 when unrestrained, are normally slightly larger than the inside diameters of'the contracted piston rings of the stack, so that each of these ring dies exerts an outward pressure against, and uniformly throughout, the back of the individual piston ring with which it engages. The metal of the heated ring, being forced between the ring dies 25 and 32, is in its austenitic state and therefore in semi-plastic condition. The die 25 forces the ring against the die 32 which in turn holds the ring against the die 25, even when the ring tends to shrink. The die 25,.being water cooled, and the die 32 being air cooled, the ring is chilled or cooled at a sufficient rate to lower the transformation temperature to such an eX- tent that a hard martensitic-condltion is, obtained when the ring reaches roomtemperature. Dur ing; this cooling cycle and prior to the transformation of the austenite to martensite, the rin while still semi-plastic, tends to shrink: in diameter, but the resilient ring die- 32v counteracts the shrinking tendency by holding the. entire face of the ring against the formed surface of the die 25.

The entire heat-forming operation could be performed by the dies 25. and-i2 permitting the piston ring to remain therebetween until the ring is fully cooled. However, in order to increase the productive capacity of the apparatus, while at the same time the piston rings are independently heat-formed, I provide the additional expanding ring dies 33. After,- a ring is formed between the dies 25 and 32 and while its metal remains in its austenitic state, it is progressively moved downward into relation. withv the. ring dies 33 which complete and fix the form of the piston ring.

The period. of time that a piston ringis, in the forming dies depends, of course, on the size of the ring and other factors as. is apparent to anyone skilled in the art. By way of example, I may say that I have satisfactorily heat-formed. 6 /3" steel rings in the apparatus illustrated by lowering the ram every seconds.

When the temperature of the ring drops to.

around400 F., the structure: of the-metal. changes from the. austenitio-state-tothe martensitic state, whereupon there is an increase in volume of the ring, which tends to cause the ring to expand. The bottom two rings of the stack (Fig, 3); are in the martensitic state and their expansion against the lower portion of the formed surface of the die- 25, holds them in position until the ram. is next opera-ted; When the lowest ring is ejected, it is substantially at room temperature.

It will be noted that each pistonring is heatformed without being affected by varying tolerances or other characteristics of the other rings of, the stackbeing operated upon. That is to say,

the formed shape is. imparted to each ring, individually and independently of the other rings.

- Thus. while a number of rings are being formed I piston rings.

at the, same time, yet some of the difficulties encountered heretofore in forming a stack of rings are avoided.

It will, also be observed that as the rings of the stack are infirm axial alignment or side contact, the rings are held flatwhile-being formed. Thed-ies themselves hold the rings firmly enough; to. accomplish; this result, no other clamping or holding means being-necessary or desired.

The process is also a. continuous one and affords high productioncapacity;

After the piston rings are, formed they are removed from the track 58 and tempered to the desired hardness.

I find that when the piston rings. are ejected 'fromthe forming mechanism, they expand, probably due to internal stresses. The expansion varies considerably so that the; diameters of the piston rings are, not uniform. I bring the rings backto their proper uniform diameter, and maintain their proper contour during the drawing operation, by the means shown in Figs. 6 and 7, as I will now explain.

A sleeve I0 has its inner periphery formed to the ultimate desired shape and diameter of the An alignment bar TI is lined by means of pins 12 to the sleeve. End plates 13 are adapted to be clamped. against the ends-of the sleeve by a bolt 14. Thepiston rings are-placed in the sleeve so that they are. in side contact with each other. I preferably do not clamp the rings such contact, but that could be accomplished,

if. desired, by the end plates E3. The gaps of the piston rings freely straddle the aligning bar ll. The fixture and the rings, mounted therein, are placed in any suitable furnace, in which the drawing operation is performed. The temperature and time of treatment vary somewhat, de: pendent upon several factors; such as the character of the. metal and the size of the piston ring. Simply by way of. example, I may say that I find that satisfactory results may be obtained by heating 6. rings, formed of steel known as S. A. E. 52100, about one hour at a temperature of about 1220 and thencooling to room temperature, while the rings remain in the fixture. The rings are cooled quickly enough to give full, hardening.

Finally, the usual finishing operations, such as sizing the gap, are performed on the rings.

Although only one. specific form of th apparatus has been illustrated in. the drawings, it will be apparentthat numerous modifications and obvious. equivalents may be. substituted without departin from the scope ofthe invention.

I claim:

1. The process of manufacturing ferrous metal piston rings which. comprises heating a split. piston ring; above the critical temperature, forcing 7 the heated ring into a forming zone and simultaneously contracting the rin to reduce the diameter thereof, confining the face of the contracted ring in said zone by a formed surface having a predetermined shape, yieldingly and uniformly exerting radial pressure throughout the back of said ring to maintain its face in such confinement, said pressure bein exerted at all points throughout the entire inner periphery of the ring at the same time, and cooling the ring below the critical temperature while so confined.

2. A continuous process for the manufacture of ferrous metal piston rings which comprises heating piston rings to above the critical temperature, forcin heated rings successively into a forming zone with the rings in the forming zone in side contact with each other, confining the faces of said rings in said zone to a predetermined shape and concurrently yieldingly exerting independent radially expanding force'throughout the entire inner periphery of each of the rings individually, said force being exerted at all points throughout the entire back of each ring at the same time,cooling the ringsoelow the critical temperature during their passage through said zone, and successively discharging the formed and cooled rings from said zone by the successive introduction into said zone of heated rings.

3. A continuous process for the manufacture of ferrous metalpiston rings which comprises heating piston rings to above the critical temperature, forcing heated rings successively into a forming zone and simultaneously contracting the rings to reduce the diameter thereof in the initial portion of said zone, confining the outer peripheries of the contracted rings in said zone to a predetermined shape, yieldingly exerting independent radially expanding force throughout the inside of each ring in subsequent portions of said zone whereby to maintain the outer periphery of each ring individually in such confinement, cooling the rings below the critical temperature during their passage through said zone, and successively discharging the formed and cooled rings from said zone by the successive introduction into said zone of heated rings.

l. An apparatus for forming piston rings while heated, comprising an outer continuous die ring havin a formed inner periphery and a split selfexpansible inner die ring disposed within said outer die ring for pressing against the inside of a heated piston ring and holding the face of the latter against the inner periphery of said outer die ring as the piston ring cools.

5. An apparatus for forming piston rings while heated, comprising an outer continuous die ring having a formed inner periphery, a split expansible inner die ring disposed within said outer die ring and having a correspondingly formed outer periphery for pressing against the inside of a heated piston ring and holding the face of the latter against the inner periphery of said outer die ring as the piston ring cools, and means providing a heat exchange coolin zone for at least one of said die rings.

6. An apparatus for forming piston rings while heated, comprising an outer female die ring having a formed inner periphery and resiliently expansible inner ring die means disposed within said outer die ring and having a correspondingly formed outer periphery normally spaced from the inner periphery of said outer die ring a distance less than the radial depth of a heated piston ring, the inner ring die means thereby being contractible by the heated piston ring whereby to exert a radial expanding force against the inner periphery of the piston ring and hold the outer periphery thereof against said formed inner periphery of said outer die ring.

7. An apparatus for forming piston rings while heated, comprisin an outer female die ring having one portion of its inner periphery tapered and another portion of its inner periphery formed to a predetermined shape, resiliently expansible inner ring die means disposed within said outer die ring and having a portion of its outer periphery tapered and another portion of its outer periphery formed to a predetermined shape, and means for moving a heated piston ring between said tapered portions and forcing it into forming position between said formed portions.

8. An apparatus for continuously forming piston rings while heated, comprising an outer die ring having its inner periphery formed to a predetermined shape and adapted to confine a plurality of piston rings, and a plurality of expansible inner die rings disposed within said outer die ring for individually pressin and holding the outer faces of the piston rings against said inner formed periphery of said outer die ring whereby a plurality of piston rings of varying radial thickness may be successively formed to the same outer diameter.

9. An apparatus for continuously formin piston rings while heated, comprising an outer die ring having its inner periphery formed to a predetermined shape and adapted to confine a plurality of piston rings, a plurality of expansible inner die rings disposed within said outer die ring for individually pressing and holding the outer faces of the piston rings against said inner formed periphery of said outer die ring, and means for moving a plurality of piston rings progressively into relationship with the inner die rings one after the other whereby a plurality of piston rings of varying radial thickness may be successively formed to the same outer diameter.

10. An apparatus for forming piston rings while heated, comprising an outer die ring having its inner periphery formed to a predetermined shape and adapted to confine a plurality of piston rings, a plurality of split, self-expanding inner die rings disposed within said outer die ring and having outer peripheries correspondingly formed to a predetermined shape for individually pressing and holding the outer faces of the piston rings against said inner formed periphery of said outer die ring, and means for moving a plurality of piston rings progressively into relationship with the inner die rings one after the other, said inner die rings being provided with inclined surfaces adjacent the formed outer peripheries thereof whereby to permit said movement of the piston rings without interference between the piston rings and said inner die rings.

11. An apparatus for formin split piston rings while heated, comprising an outer die ring having its inner periphery formed to a predetermined shape, a plurality of split expanding inner die rings spaced from and in the zone of said formed inner periphery, said inner die rings being in free side contact with each other and having outer peripheries correspondingly formed to said shape for individually pressing and holding the outer faces of a plurality of piston rings against the inner formed periphery of said outer die ring, feeding means disposed adjacent said die rings for movin a plurality of piston rings progressively into relationship with the inner die rings one after the other, the lower piston ring within the outer die ring being in engagement with only the outer die ring and being held in that position by its own pressure until ejected from the inner die ring, and ring-closing means disposed between said feeding means and said die rings for contracting the diameter of a heated split piston ring as it is moved into contact with said formed inner periphery.

12. An apparatus for forming piston rings while heated, comprising an outer die ring and at least one inner ring die means disposed therein to provide a channel therebetween into which piston rings are moved, a shiftable guiding and ringclosing element having an opening with a taper and disposed adjacent the inlet to said channel, means for limiting the shiftable movement of said element, and means adjacent said element for engaging and moving a piston rin placed in the taper of said opening for closing the piston ring and forcing it into said channel.

13. An apparatus for forming piston rings while heated, comprising an outer die rin and at least one inner ring die means disposed therein to provide a channel therebetween into which piston rings are moved, a ring-closing and guiding element disposed adjacent the inlet to said channel and having an opening with the mouth portion tapered and the exit portion formed to a predetermined shape, and an operating device having a ring portion formed substantially to said predetermined shape and adapted to engage and move a piston ring from said mouth portion into said channel.

14. An apparatus for forming split piston rings while heated, comprising an outer die ring having its inner periphery formed to a predetermined shape, a plurality of split expandin inner die rings spaced from and in the zone of said formed 10 inner periphery, said inner die rings being in free side contact with each other and having outer peripheries correspondingly formed to said shape for individually pressing and holding the outer faces of a plurality of piston rings against the inner formed periphery of said outer die ring, a shiftable guiding and ring-closing element having a tapered opening and disposed adjacent said die rings for contracting the diameter of a heated split piston ring, means cooperating with said element for limiting the shiftable movement thereof, and ring-feeding means disposed adjacent the opening of said element for moving a plurality of piston rings progressively through said element into relationship with the inner die rings.

JOSEPH C. LINN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Marien et a1 Mar. 29, 1949 

